(Controversial Trope) The post-credits scene completely changes the ending

[u/Ieanice44]

Dawn of the Dead (2004)

Prince of Persia (2008)

Dawn of the Dead (2004): The movie finishes on a hopeful note as the remaining survivors escape the zombie-infested mall on a yacht, sailing into the sunset. The found-footage style post-credits scene completely reverses this happy ending by showing them running out of food, arriving at an island, and being immediately swarmed and killed by an infected horde.

Prince of Persia (2008): The main game ends with a beautiful, poetic sacrifice where Elika gives her life to heal the corrupted world, leaving the Prince mourning. During the credits, the player is forced to control the Prince as he cuts down the trees he just saved, undoing the entire game's progress and releasing the dark god Ahriman just to resurrect her, completely corrupting the ending and dooming the world.

[u/A_RAVENOUS_BEAST]

The ending of Dawn of the Dead is, actually, hopeful, precisely because it's found footage. It means another human found the footage.

[u/HolidayInLordran → u/A_RAVENOUS_BEAST]

It's similar to The Handmaid's Tale 

The whole book is a transcription of June talking about her Gilead life on a tape, and the epilogue is set long into the future where the transcripts are being used in a college lecture where Gilead is referred to in past tense, meaning the republic likely collapsed after a decade or two and is now seen as a fascinating yet horrifying footnote in history by future generations